1. Field of the Invention
This invention relates cantilevers embedded with sensors on surface and integrated amplification circuitry responding to deflection of the cantilever useable in magnetic disk drives, magnetic force microscopes, magnetic resonance force microscopes, accelerometers, and other systems where a sensing of a mechanical deflection is involved.
2. Brief Description of the Prior Art
A number of cantilever sensors have been patented recently and commercial models of these sensors are now available in microminiature form. All of these cantilever sensors use passive detectors to sense the deflection of the free end of the cantilever. For example, the cantilever magnetometer developed by Naughton and Chaparala (AIP conference proceedings #273, p.407, 1992, "Capacitance Platform Magnetometer for thin film and small crystal superconductor studies and U.S. Pat. N0. 5,739,686, the disclosure of which is incorporated herein, by reference, as though recited in full) consists of two capacitor plates, one of which is roughly Five microns thick, and machined out of a silicon wafer. The two plates are glued together to a sample platform with the top plate free to bend as a cantilever. This cantilever design has been used in the sensitive measurements of the magnetic properties of materials in very high fields and over a very broad temperature range. In these measurements, a small piece of a magnetic sample is glued to the free end of the cantilever. Any external magnetic field acts on the magnetic sample and causes the cantilever to deflect and thus change the capacitance. However, this cantilever design and the capacitance method of detecting the deflection of the cantilever suffers from the drawback that it is not possible to determine whether it is the force or the torque acting on the magnetic sample that is causing the deflection of the cantilever tip.
Another example of an existing cantilever sensor is the Atomic Force Microscope (AFM) cantilever of Albrecht et. al. (U.S. Pat. N0. 5,483,822), the disclosure of which is incorporated herein, by reference, as though recited in full, and Applied Physics Letters, 62, p.634, 1993, "Atomic Resolution with an Atomic Force Microscope with Piezoresistive Detection"). Here, the deflection of the cantilever is obtained by measuring the change in the resistance of a layer of doped silicon on the cantilever which itself is micromachined from a block of single crystal silicon. This design also suffers from the inability to distinguish between a force and a torque signal and furthermore requires external amplification circuitry to magnify the effects of the change in the resistance of the doped silicon layer.
Additional background as to cantilevers with piezoresistive deflection sensors are found in U.S. Pat. Nos. 5,345,815 and 5,595,942, the disclosures of which are incorporated herein, by reference, as though recited in full.